The evolution of computer technology has resulted in the creation of a sophisticated technical area devoted to the representation of graphics information generated by computers. This area is termed computer graphics. One graphics technique commonly used to produce an image is that of producing a set of points and connecting these points with straight lines. The resulting combination of points and straight lines are displayed on the computer graphics terminal display which normally includes a cathode ray tube (CRT). The cathode ray tube includes an array of picture elements. The graphics image is produced by illuminating selected picture elements of the array. This array of picture elements in a display corresponds to the memory locations in an image memory. This image memory is often termed a bit map memory. The corresponding CRT display is termed a bit mapped display.
A very useful function for bit map displays is the ability to move a rectangular block of illuminated picture elements (pels) from one place in the bit map (or display) to another place and to logically combine two subsets of the image array to produce a third image array. Another useful function is that of drawing lines between two points. The technique often used to draw these lines is disclosed in a text entitled Fundamentals of Interactive Computer Graphics by James D. Foley and Andries Van Dam published by Addison Wesley Publishing Company, 1982 and herein incorporated by reference.
Discussions of graphic functions are contained in several IBM Technical Disclosure Bulletins. IBM Technical Disclosure Bulletin, Vol. 28, No. 6, November 1985, entitled "Graphic Bit-Blt Copy Under Mask" discloses a system for making bit boundary block transfers of arbitrary shapes within a frame buffer. IBM Technical Disclosure Bulletin, Vol. 27, No. 8, 1985, entitled "Raster Graphics Drawing Hardware", describes the application of programmable logic arrays to the design of hardware circuitry implementing graphics drawing algorithms. IBM Technical Disclosure Bulletin, Vol. 28, No. 5, October 1985, entitled "Circuit for Updating Bit Map-Memory of A Display Adapter", discloses a circuit for providing bit manipulation flexibility to control picture element data stored in an all points addressable display memory.
An object of the present invention is to provide a controlling mechanism for an graphics processor and an graphics memory for rapidly accomplishing bit block transfers and line draw functions.